1. Field of the Invention
The present invention relates to a thermoplastic resin composition, a molding made of the thermoplastic resin composition and a process of making the molding.
2. Description of Related Art
In the recent years, as having been known in, for example, the field of automobile vehicles, there is a strong demand on resin moldings such as used for interior parts of a passenger compartment for higher impact absorption in order to enhance passenger protection function upon an occurrence of a collision. Thermoplastic resins such as polypropylene have been known as the high impact absorptive material suitable for the interior parts.
In order to enhance the impact absorption of such a thermoplastic resin molding, various kind of things have been done to meliorate thermoplastic resin compositions for an increase in the property of elongation thereof. For example, it has been attempted to disperse an elastomer component such as a rubber component in a resin matrix such as a polypropylene resin so that the elastomer component causes deformation due to an impact load. A thermoplastic resin molding made of the thermoplastic resin composition provides an improvement in the property of elongation, in particular the property of high speed elongation at a loading speed of higher than 2 m/sec., of the thermoplastic resin molding.
As just described above, although the property of elongation of a thermoplastic resin molding can be meliorated to a certain extent by dispersing an elastomer component in a matrix resin for the thermoplastic resin molding, what can not be overlooked is the problem that a thermoplastic resin molding demonstrates a tendency to toward a decline in the coefficient of elasticity, in particular a decline in the flexural coefficient of elasticity, in the case of trying to increase the elastomer content of the thermoplastic resin composition in order to realize a more enhanced property of elongation of the thermoplastic resin molding. Although an enhancement of the property of elongation of the thermoplastic resin molding could conceivably include a change in the type of elastomer of the thermoplastic resin composition, however, when the elastomer is of an unusual type, the elastomer itself is too expensive to be employed for the thermoplastic resin composition and turns out to be little practical.
In the way of ensuring an enhancement of the property of elongation of a thermoplastic resin molding by melioration of the thermoplastic resin composition, in the event where, even though a trial molding works out satisfactorily, there occurs the necessity of changing the composition of the thermoplastic resin material for the molding for some reasons in subsequent events, the thermoplastic resin material generally changes its solid state properties such as a coefficient of contraction resulting from the change in composition. This causes the necessity of modifying the molding die or fabricating an alternative molding die which drives up a molding cost.